1. Field of the Invention
The present invention relates to a manufacturing method of a camera module for use in an image pickup apparatus or the like.
2. Description of the Related Art
Variously configured products of an image pickup module, on which an image pickup element such as a CCD or a CMOS is mounted, have been provided (see, for example, JP-A-2003-60177, JP-A-2004-147032 and JP-A-08-271782) . FIGS. 1A and 1B show an example of a camera module assembled by screwing a lens holder 11, which holds a light receiving lens 12, into a barrel portion 10a of a body holder 10. This camera module is assembled as follows. That is, first, an infrared ray cut glass filter 13 is attached to the inner surface of the casing portion 10b so as to seal an opening hole 10c of the barrel portion 10a. Thereafter, a substrate 20, on which an image pickup element 21 is mounted, is bonded to an opening end surface of the casing portion 10b with an adhesive.
Incidentally, a lens holder 11 is screwed into the barrel portion 10a of the body holder 10 through a spacer 14 made of silicon rubber. A stopper portion 10d is provided on the inner peripheral surface of the barrel portion 10a, which is connected to the casing portion 10b. The spacer 14 is mounted in the barrel portion 10a by being sandwiched between end surfaces of the stopper portion 10d and the lens holder 11. The spacer 14 is used to prevent the lens holder 11 from turning in a state in which the lens holder 11 is screwed into the barrel portion 10a, and also used to hold the lens holder 11, that is, the light receiving lens 12 at a predetermined focus position.
In the aforementioned camera module assembled by screwing the lens holder 11 into the barrel portion 10a, in order to correctly place the light receiving lens 12 at the focus position, the lens holder 11 having been being screwed into the barrel portion 10a is turned around an axis thereof to adjust the position in the direction of an optical axis of the lens holder 11. Thus, an adjusting operation of positioning the light receiving lens 12 at the focus position is performed.
FIG. 2 illustrates a manner in which focus adjustment is performed by turning the lens holder 11, which mounted in the barrel portion 10a, through the used of an adjusting piece 30 for focus adjustment. A light receiving penetration hole 11a is provided in a central portion of an end surface 110 of the lens holder 11. Engaging grooves 11b are provided at four places around the penetration hole 11a by being disposed at uniform circumferential intervals. Hooks 31 to be respectively caught by the engaging grooves 11b are provided at four places in the adjusting piece 30 by being disposed at uniform circumferential intervals, similarly to the engaging grooves 11b. Thus, the hooks 31 are engaged with the engaging grooves 11b, respectively, and the adjusting piece 30 is turned. Consequently, the focus adjustment can be performed.
Meanwhile, in order to check whether or not the spacer 14 is correctly mounted in the barrel portion 10a, the following checking operation is performed in the camera module shown in FIGS. 1A and 1B also as an operation of screwing the lens holder 11. That is, when an operation of screwing the lens holder 11 into the barrel portion 10a, the screwing operation is stopped at a moment at which a predetermined amount of torque acts thereon. Then, the height of an end surface 110 of the lens holder 11 (that is, the position of the sunk lens holder 11) at that time is checked to inspect whether or not the spacer 14 is mounted in the barrel portion 10a. 
In the operation of checking whether this spacer 14 is mounted in the barrel portion 10a, the screwing of the lens-holder 11 is stopped by detecting the value of turning-torque of the lens holder 11. Thus, the position (in the direction of rotation of the lens holder 11), at which the lens holder 11 is stopped, varies according to variation in the quality of the product.
Incidentally, an operation of screwing the lens holder 11 into the barrel portion 10a is performed by using a screwing piece provided with hooks, which is slimier to the adjusting piece 30. FIGS. 3A to 3D illustrate an example of a case where the lens holder 11 stops in a state, in which the lens holder 11 is screwed into the barrel portion 10a, and in which the position in the direction of rotation of the lens holder 11 changes variously.
Because the position in the direction of rotation of the lens holder 11 changes variously, in the focus adjustment operation of the lens holder 11, first, the adjusting piece 30 is once rotated (about 90 degrees or more) in a direction opposite to a screwing direction. Then, the hooks 31 are engaged with the engaging grooves 11b. Also, the lens holder 11 is slightly turned in a direction in which the lens holder 11 is loosened. Subsequently, the focus adjustment is performed by rotating the lens holder 11 in a screwing direction (a positive rotation direction). The reasons for rotating the lens holder 11 in the positive rotation direction after the adjusting piece 30 is reversely rotated are that the hooks 31 of the adjusting piece 30 are surely engaged with the engaging grooves 11b, and that the lens holder 11 passes through a focus point and the focus adjustment cannot appropriately be achieved in a case where the lens holder 11 is rotated in a screwing direction from the beginning.
Thus, in the related-art process of assembling a camera module, at the focus adjustment, the adjusting piece 30 is once reversely rotated to thereby slightly loosen the lens holder 11. Then, the position of the lens holder 11 is adjusted to the focus point. Therefore, an operation of turning the adjusting piece 30 is made to be cumbersome. Consequently, the related-art method has a drawback in that the productivity of the camera module is reduced.